Material Compatibility and the Human Body

Introduction It is fascinating to watch the spider at work building its web. One may often wonder where the spider obtains the silk material it uses. This material is a soluble silk protein solution formed inside the spider, which changes into an insoluble natural high-performance protein fiber outside the spider. Scientists have found that the primary constituents of the spider silk (biological material) are two simple amino acids, glycine and alanine. These biomaterials have attracted much interest from scientists, because it is feasible to produce the spider silk proteins. Our simple knowledge of the spider's dragline means that we can produce materials that have excellent mechanical properties and are biocompatible; that is, the body perceives the tissue or other material as non-foreign and accepts it as part of the body. We can also coat materials such as metals, plastics, ceramics, and composites with biocompatible materials. Although the use of this family of materials to repair the human body has been recorded for centuries, advances in the science of biomaterials have enabled doctors, more than ever before, to replace body parts that are nonfunctional (Agrawal, 1998). Typically, implantable materials are classified as polymers, ceramics, metals, and composites. Of these materials, the most widely used for implants are titanium, polyethelene, tricalcium phosphate, and hydroxyapatite (Johnston, et. al, 1999). When biomaterials are introduced to the human body, there are varieties of interactions with the new biological environment, especially with the material's contact with blood and tissue, which sometimes results in the body's rejection of such material. Metallic biomaterials, for example, are generally used for replacement of structural components of the human body where considerable strength or carrying weight is required, such as in most orthopedic implants (hip and knee joints). The metal sometimes corrodes or wears off, releasing metal ions and debris, which may have a toxic effect on tissue (Yamamoto, Honma & Sumita, 1997). One major challenge for biomaterial scientists is to study or understand the toxicity of the materials they use in order to eliminate complications that may arise as a result of toxic materials in the body systems. The Biomaterials Tissue and organ failure resulting from injury or other damage is a major health concern. Treatment options include transplantation, surgical repair, implanting artificial prostheses, and mechanical devices (Persidis, 1999). Biotechnology has allowed for alternative or complementary solutions to numerous health problems. Biotechnology is the use of biochemicals, cells, or parts of living organisms to make products or modify existing ones. The technology allows us to build or change the nature of materials so that they can be used inside the human body. The secret for our body's adapting to a foreign material is the ability of the material to be compatible to the human body and also support tissue growth. Biomaterials for implants have to display a wide range of adaptability to suit the various stages of the bio-integration process of any foreign material that is introduced into the human body. Biomaterials are substances other than food or drugs contained in therapeutic or diagnostic systems that are in contact with tissue or biological fluids, as replacement for soft and hard tissues, for example adhesives and dental materials (Peppas & Langer, 1994). The development of new tissue will rely on biomaterials that physically support tissue growth and stimulate specific cell functions. Such materials combined with inherent biological properties have been shown to improve the regeneration of several tissues including bone and nerve, which can specifically trigger desired cell responses (Collier, Camp, Hudson, & Schmidt, 2000). Sometimes it is necessary to combine materials in order to achieve this purpose (Wang, Khor & Cheang, 1998). …